1. Field of the Invention
The present invention relates to a measuring apparatus that applies centrifugal force to a sample for carrying out a measurement. More particularly, it relates to a measuring apparatus that is applicable to a measuring instrument used in a blood test and the like, for example, which centrifugally separates a blood sample and analyzes blood components being obtained.
2. Description of the Related Art
In a blood test in the field of clinical diagnosis, a disease state of a subject, a recovery condition after treatment, and the like are grasped, by means of analyzing a specific component of the blood being collected. Generally, in the blood test as described above, the blood being collected is separated by component, and analysis is conducted only on the component containing a substance to be analyzed. In many cases, a serum component is considered as a target item for checking in a biochemical examination of blood.
In measuring and analyzing a sample such as blood, there is known a measuring apparatus that centrifugally separates components contained in the sample by using centrifugal force, so as to measure a component being separated. For instance, the blood being collected is subjected to a centrifugal separation, to obtain blood serum and the like by separating erythrocyte, leucocyte, lymphocyte, platelet, and blood coagulation factors, and the blood serum and the like are each taken into test tubes. Then, with respect to each, concentration of pH, oxygen, carbon dioxide, and the like, are measured by a chemical sensor. In addition, a test reagent such as enzyme is injected and an emission reaction with a substrate in the blood serum is subjected to spectroscopy or absorption spectroscopy (for example, see Japanese Unexamined Patent Application Publication No. 2003-107080, paragraphs 0002 and 0020, hereinafter, referred to as “patent document 1”).
In addition to the above method where the component centrifugally separated is injected in each test tube and the analysis is conducted therein, there is also known a technique for the blood analysis, which uses an apparatus called a biosensor. This biosensor has a structure to collect a sample and also transport the sample being collected to an analysis part. Centrifugal force is applied to the biosensor while keeping the sample inside, thereby transporting the sample being collected to the analysis part within the biosensor, and further the sample is subjected to the centrifugal separation within the analysis part. Furthermore, as a way of example, a reagent may be provided within the analysis part, enabling an analysis by reaction of a component with the reagent.
As a representative example of testing equipment used for examination at home, a device for SMBG (Self Monitoring of Blood Glucose) has been developed, which measures glucose concentration in blood (blood glucose level). In the examination employing the SMBG device broadly used these days, the subject oneself stabs a fingertip or an arm with paracentesis needle, and a small amount of blood sample having bled is utilized.
To be exact, the blood glucose level indicates glucose concentrations in the serum. The most common method for measuring the glucose concentrations is the one which utilizes an enzyme electrode. In this measuring method, a whole blood sample being collected is fed into a biosensor, and it is subjected to a measurement. The biosensor has an enzyme reaction layer inside. According to an amperometric measuring method, the enzyme reaction layer measures a current in accordance with the glucose concentration in the serum without hemolyzing the blood cell. In this measuring method, the concentration of a particular component in the serum is measured without separating the blood cell component.
Japanese Unexamined Patent Application Publication No. 2002-310973, pages 6 to 8, hereinafter, referred to as “patent document 2”, discloses an electrochemical biosensor as a simple instrument for measuring blood glucose level, which measures the glucose concentration in the whole blood sample collected from human. This biosensor is provided with a suction port for sucking a sample, and when the whole blood sample as a sample is provided to this suction port, the whole blood sample is sucked into a suction cavity called as a capillary fill chamber, by means of capillary phenomenon. This sucking into the suction cavity is performed by letting the air in the suction cavity out of a vent hole which is formed in the recesses of the suction cavity.
A working electrode and a counter electrode are arranged in this suction cavity. These electrodes obtain a measured current value being correlated with the glucose concentration, in a condition that the whole blood sample includes a blood cell component. Based on this measured current value, the blood glucose level can be measured easily.
Japanese Unexamined Patent Application Publication No. 2004-109082, pages 6 to 9, hereinafter, referred to as “patent document 3”, discloses a biosensor for blood analysis which performs a plasma separation by centrifugal operation. A flow channel of the biosensor for blood analysis is provided with a portion where a blood cell component is accumulated in the centrifugal direction upon centrifugal separation. With the centrifugal separation, the blood cell component is accumulated on the bottom, and a plasma component is separated as supernatant. In order to introduce the whole blood sample obtained from the subject as a sample, this biosensor is provided with an external pump at an outlet port, and the whole blood sample is suctioned by the suction negative pressure from the blood suction port. Similarly, it is also configured such that the plasma component after the centrifugal separation is transferred to an analytical position by the suction negative pressure from the external pump. In addition, the blood analyzer disclosed in the patent document 1 includes a configuration to apply centrifugal force by rotating the biosensor having an electrode, and the electrode of the biosensor is brought into electrical contact with a point of contact.
In the blood analyzer disclosed in the patent document 1 as described above, the biosensor is mounted on a rotary table, and centrifugal force is applied to the biosensor by turning this rotary table. There is also a configuration that an opening is provided on the rotary table to establish electrical connection with the electrode of the biosensor, and a contact for measurement is made to move up and down through this opening part.
In this configuration, when the rotary table is to be rotated, the contact for measurement is moved down, and centrifugal force can be applied to the biosensor by turning the rotary table without an interference with the contact. When the measurement is performed, the rotary table is brought to a halt, then, the contact for measurement is raised by passing through the aforementioned opening, and electrical connection is established with the electrode of the biosensor.
According to this configuration, both application of centrifugal force and measurement via the electrode, targeting a sample taken into the biosensor, can be performed within one biosensor. Therefore, an operation to move the sample is unnecessary, thereby achieving a configuration suitable for an automatic analysis.
In the measuring device using centrifugal force, electrical connection between the contact for measurement and the electrode of biosensor is necessary, when the measurement is carried out. Generally, when the rotary table is stopped having been rotating at a high speed, without any control, a position where the rotary table being stopped is random in the circumferential direction. Therefore, in the above configuration for measurement, generally, the stop position of the contact for measurement is not always opposed to the electrode of the biosensor. It is thus required to align the contact for measurement with the position being opposed to the electrode of the biosensor.
FIG. 20A to FIG. 20D are illustrations to explain a positional relationship between the contact for measurement and the electrode of the biosensor in the conventional measuring device utilizing centrifugal force. FIG. 20A illustrates that the biosensor 111 is being mounted on the rotary table 102. The biosensor 110 is fixed on and held by a retainer 103 that is provided on the board face of the rotary table 102. The biosensor 110 receives centrifugal force generated by turning the rotary table 102 rotatably supported by the rotary shaft 101, and the sample stored inside is centrifugally separated (FIG. 20B). After the centrifugal separation is finished, the turning of the rotary table 102 is brought to a halt. Then, the rotational position of the rotary table is adjusted for alignment, whereby the electrode 111 of the biosensor 110 is electrically connected to the contact for measurement 104 (FIG. 20C). In the state where the electrode 111 of the biosensor 110 and the contact for measurement 104 are electrically connected, the electrode 111 is energized and simultaneously a measured current is checked (FIG. 20D). In order to establish the electrical connection between the electrode 111 of the biosensor 110 and the contact for measurement 114, alignment is necessary at the time of halt as shown in FIG. 20C.
As a way of example to align the contact for measurement with a position opposed to the electrode of the biosensor, there is a configuration to install a controller to control the rotation of the rotary table, or a configuration to employ a stepping motor.
However, installation of such controller to control the rotation may be a factor that increases the cost of the device. This rise in cost by installing the controller may become more pronounced, as a rotating speed of the rotary table is set to be higher. If the stepping motor is employed, it is possible to control the stop position, but the rotating speed is hardly set to be high. Therefore, it is not applicable when large centrifugal force is to be applied.
In order to address the problems as described above, an object of the present invention is to provide a simple configuration which both applies centrifugal force to the biosensor and establishes electrical connection with the electrode of the biosensor. The present invention further aims at establishing connection between the electrode of the biosensor and the measuring part, without an alignment of the rotational position of the rotary table.